The present invention generally relates to gettering materials and devices for gettering gases, such as within a gas stream or a closed chamber. More particularly, this invention relates to gettering devices capable of being more versatile and/or more reliable in a variety of applications.
The use of certain materials to remove or “getter” gases is a well-known technique for improving the performance of devices whose operations require or benefit from an evacuated enclosed volume or space or the selective removal of one or more particular gas species. As used herein, a getter material is a composition that absorbs, reacts, or otherwise combines with gas molecules to remove the gas molecules from a flowing gas stream (in which case the getter may be called a filter) or a sealed and typically evacuated chamber (in which case the getter is employed to lower or maintain low pressures and improve the performance of a device containing or operating within the chamber). Representative getter applications include micromachined devices (for example, MEMS wafers), vacuum tubes, cathode ray tubes, vacuum display devices, flat panel displays, resonant sensors, tunneling sensors, flow sensors, motion sensors (for example, inertial sensing platforms, angular rate sensors, and accelerometers), gyroscopes (including resonating gyroscopes and fiber optic gyroscopes (FOG)), pressure sensors, infrared (IR) sensors, chemical sensors, atomic interferometer (AI) sensors, resonators, ion accelerators, lighting devices, gas filters, solid-state vacuum pumps, micro-mirror arrays, personal protection air purification systems (for example, gas masks), density meters, rf-resonators for communication devices (for example, RF-MEM's), gas purification systems, atomic and resonant clocks, semiconductor equipment, scientific vacuum systems (for example, particle accelerators and analysis tools), etc. When employed for displays and optical sensor applications, getter materials are typically opaque metal films, particles, strips or pellets whose placement must then be controlled to avoid blocking the emission or transmission of the radiation of interest, such as infrared, optical, radio, etc.
Getters are typically employed in the form of evaporated films, sputtered films, and sintered non-evaporable getters (NEG's) such as pellets and strips. Oxygen, air, and water vapor are typically gettered (reacted) with chemically active or reactive metals or alloys, such as Ba, Mg, Ti, Zr, Fe, Cr, Ca, etc. In contrast, organic gases are typically gettered (absorbed) by activated charcoal, silica, or zeolite. Under some circumstances, such as when one or more organic gases and oxygen, air, and/or water vapors require gettering, multiple different getter materials must be employed.
Once enclosed in a vacuum or otherwise placed in the space to be gettered, getter materials often must be “activated,” by which absorbed gas molecules are desorbed and/or oxidation and surface contaminates are removed, such as by a high temperature vacuum bake, chemical etch, or exposure to a forming or reducing gas such as hydrogen or a carbon-based reducing gas. The life of a getter material is typically limited in that the chemical reactivity or absorbent qualities of getter materials decline over time as the getter gas molecules combine or absorb onto the surface of the getter. If the capacity of the getter material is exceeded, the getter will no longer remove the gases of interest, necessitating (if possible) regeneration of the getter material through an additional activation treatment.